Light source for plant cultivation

ABSTRACT

A light source of a plant cultivation is turned on or turned off depending on a light period and a dark period of a plant, and the light source of the plant cultivation is turned on in the light period and emits a light having a spectrum with a plurality of peaks to the plant to increase a content of a predetermined substance in the plant.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of United States ProvisionalApplications No. 62/722,389, filed on Aug. 24, 2018, and No. 62/870,905,filed on Jul. 5, 2019, which are hereby incorporated by reference forall purposes as if fully set forth herein.

BACKGROUND 1. Field of Disclosure

The present disclosure relates to a light source for plant cultivation.More particularly, the present disclosure relates to a light source thatemits a light optimized for plant photosynthesis.

2. Description of the Related Art

Various light sources replacing sunlight are being developed and beingused as lighting for plant cultivation. Conventionally, incandescentlamps and fluorescent lamps are mainly used as the lightings for plantcultivation. However, the conventional lightings for plant cultivationprovide light having a specific wavelength to plants for only thepurpose of plant photosynthesis, and most of them do not have anyadditional functions.

Plants synthesize substances useful to humans while resisting a varietyof stress factors, and there is a need for a light source, a cultivationdevice, and a cultivation method to cultivate plants that contain alarge amount of substances useful to humans.

SUMMARY

The present disclosure provides a light source capable of cultivating aplant containing a large amount of substances useful to humans. Thepresent disclosure provides a cultivation device capable of easilycultivating the plant using the light source. The present disclosureprovides a cultivation method capable of easily cultivating the plantusing the light source or the cultivation device.

Embodiments of the present disclosure provide a plant cultivation lightsource being turned on or turned off depending on a light period and adark period of a plant. The plant cultivation light source is turned onin the light period and emits a light having a spectrum with a pluralityof peaks to the plant to increase a content of a predetermined substancein the plant. When a portion of the light period is referred to as afirst period and the other portion of the light period is referred to asa second period, at least one peak of the peaks of the light emitted inthe second period of the light period is not provided in the firstperiod preceding or following the second period, and the other peaksappear at substantially the same wavelength in the second period and thefirst period except for the at least one peak provided in the secondperiod and not provided in the first period.

The at least one peak provided in the second period and not provided inthe first period appears at a wavelength equal to or smaller than about300 nm. The at least one peak provided in the second period and notprovided in the first period has a wavelength of about from about 280 toabout 295. The second period is shorter than the first period, or thesecond period is less than about 6 hours. The light is continuouslyemitted from the light source during the second period.

The dark period and the light period are repeated on a 24-hour basis, ora daily basis.

The predetermined substance includes at least one of chlorophylls,flavonols, and anthocyanins. The other peaks except for the at least onepeak provided in the second period and not provided in the first periodare provided in a visible light wavelength band. The other peaks exceptfor the at least one peak provided in the second period and not providedin the first period include peaks respectively provided in a bluewavelength band and a red wavelength band.

The light source includes a plurality of light emitting diodes emittinglights having different wavelengths from each other. The light emittingdiodes include a first light emitting diode providing the lightcorresponding to the at least one peak provided in the second period andnot provided in the first period and a second light emitting diodeproviding the light corresponding to the other peaks except for the atleast one peak.

According to an embodiment of the present disclosure, the light sourceis employed in a plant cultivation device, and the plant cultivationdevice includes a housing in which a plant is provided, a light sourceprovided in the housing to irradiate a light to the plant, and acontroller controlling the light source.

Embodiments of the present disclosure provide a method of cultivating aplant using the light source including germinating a seed of the plant,growing the germinated seed to a sprout, transplanting the sprout togrow the sprout to an adult plant, and irradiating a light to the adultplant right before harvesting the adult plant to increase a content of apredetermined substance in the plant. The irradiating of the lightbefore harvesting the adult plant includes emitting a light having aspectrum with a plurality of peaks to the plant in a light period. Whena portion of the light period is referred to as a first period and theother portion of the light period is referred to as a second period, atleast one peak of the peaks of the light emitted in the second period ofthe light period is not provided in the first period preceding orfollowing the second period, and the other peaks except for the at leastone peak provided in the second period and not provided in the firstperiod appear at substantially the same wavelength in the second periodand the first period.

According to the above, the plants may be efficiently cultivated usingthe light source, and the content of the substances useful to humans mayeasily increase in the plants.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

The above and other advantages of the present disclosure will becomereadily apparent by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1A is a plan view showing a light source for plant cultivationaccording to an exemplary embodiment of the present disclosure;

FIG. 1B is a block diagram showing a light source module for plantcultivation according to an exemplary embodiment of the presentdisclosure;

FIG. 2 is a cross-sectional view showing a light emitting device,according to an embodiment of the present disclosure;

FIGS. 3A to 3C are graphs showing a spectrum of a light emitted from alight source according to an exemplary embodiment of the presentdisclosure;

FIG. 4 is a view showing growth conditions of kale according to anexperimental example;

FIG. 5 is a view showing experimental conditions in an exemplaryembodiment;

FIGS. 6A to 6C are graphs sequentially showing contents of chlorophylls,flavonols, and anthocyanins contained in kale harvested on the 31st dayafter the date of sowing, after the light treatment was performed incomparative example 1, experimental example 1, and experimental example2;

FIG. 7 shows experimental conditions in an exemplary embodiment;

FIGS. 8A to 8D are photographs showing experimental results ofcomparative example 2, experimental example 3, and experimental example4, respectively;

FIGS. 9A to 9C are graphs sequentially showing contents of chlorophylls,flavonols, and anthocyanins contained in kale harvested on the 31st dayafter the date of sowing in comparative example 2, experimental example3, and experimental example 4, respectively;

FIG. 10 shows experimental conditions in an exemplary embodiment;

FIGS. 11A and 11B are photographs showing experimental results ofcomparative example 3, experimental example 5, and experimental example6;

FIGS. 12A to 12C are graphs sequentially showing contents ofchlorophylls, flavonols, and anthocyanins contained in kale harvested onthe 31st day after the date of sowing, after the light treatment wasperformed in comparative example 3, experimental example 5, andexperimental example 6;

FIG. 13 shows experimental conditions in an embodiment;

FIGS. 14A to 14D are photographs showing experimental results ofcomparative example 4, experimental example 7, and experimental example8;

FIGS. 15A to 15C are graphs sequentially showing contents ofchlorophylls, flavonols, and anthocyanins contained in kale harvested onthe 31st day after the date of sowing, after the light treatment wasperformed in comparative example 4, experimental example 7, andexperimental example 8;

FIG. 16 shows experimental conditions in an embodiment;

FIGS. 17A to 17C are graphs sequentially showing contents ofchlorophylls, flavonols, and anthocyanins contained in tatsoi, mustard,and broccoli harvested on the 31st day after the date of sowing, afterthe light treatment was performed in comparative examples andexperimental examples according to the experimental conditions of FIG.16;

FIGS. 18A to 18C are photographs showing the experimental results of thecomparative example and the experimental example according to theexperimental conditions of FIG. 16; and

FIG. 19 is a perspective view conceptually showing a cultivation deviceaccording to an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

The present disclosure may be variously modified and realized in manydifferent forms, and thus specific embodiments will be exemplified inthe drawings and described in detail hereinbelow. However, the presentdisclosure should not be limited to the specific disclosed forms, and beconstrued to include all modifications, equivalents, or replacementsincluded in the spirit and scope of the present disclosure.

Like numerals refer to like elements throughout. In the drawings, thethickness, ratio, and dimension of components are exaggerated foreffective description of the technical content. It will be understoodthat, although the terms first, second, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms are only used to distinguish oneelement, component, region, layer or section from another region, layeror section. Thus, a first element, component, region, layer or sectiondiscussed below could be termed a second element, component, region,layer or section without departing from the teachings of the presentdisclosure. As used herein, the singular forms, “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise.

It will be further understood that the terms “comprises” and/or“comprising”, or “includes” and/or “including”, when used in thisspecification, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

The present disclosure relates to a light source used to cultivateplants. Plants photosynthesize using a light in a visible lightwavelength band and gain energy through photosynthesis. Photosynthesisof plants does not occur to the same extent in all wavelength bands. Thelight in a specific wavelength band that the plants use forphotosynthesis in sunlight is called Photosynthetic Active Radiation(PAR), occupies a portion of solar spectrum, and corresponds to a bandfrom about 400 nanometers to about 700 nanometers. The light source forplant cultivation according to an exemplary embodiment of the presentdisclosure includes the light in the PAR wavelength band to provide anappropriate light for plant photosynthesis, and the light source forplant cultivation provides a light in a wavelength band to increase thecontent of ingredients (hereinafter, referred to as an “activeingredients”) that positively affect the health of humans or the plantsupon ingestion. In this case, the active ingredients are substancesknown to be necessary for humans, such as chlorophylls, flavonols,anthocyanins and glucosinolates.

Chlorophylls are known as a photosynthetic pigment of green vegetablesand help to prevent bad breath and constipation. Flavonols areantioxidants and include quercetin, kaempferol, and myricetin as itsrepresentative substances. Quercetin is an antioxidant with highantioxidant capacity, Kaempferol is known to prevent cancer cellproliferation by enhancing immunity, and Myricetin is known to inhibitthe accumulation of fat to prevent cardiovascular disease. Anthocyaninsare one of the representative antioxidants and have the effect ofpreventing aging by removing reactive oxygen species in human body.Anthocyanins also help re-synthesis of a pigment called rhodopsin in theeye's retina to prevent eye strain, decreased visual acuity, cataract.

When the glucosinolates are absorbed into human intestines, theglucosinolates may be degraded by intestinal microorganisms andconverted to isothiocyanate. The glucosinolates are known to beeffective against cancer and is effective for bladder cancer, breastcancer, and liver cancer. In particular, the glucosinolates have asuperior ability to regulate leukocyte and cytokine and have an enzymethat inhibits tumor growth in breast, liver, colon, lung, stomach, andesophagus. In addition, it is known that indole-3-carbinol produced bythe glucosinolates also has an anticancer activity.

The glucosinolates may be a substance represented by the followingchemical formula 1, and R may be various functional groups. R may be,for example, substituted or unsubstituted allyl, benzyl, or2-phenylethyl group with from 1 to 10 carbon atoms.

In the exemplary embodiment of the present disclosure, depending on thetype of R, the glucosinolates may be glucoerucin, glucoraphenin,gluconapin, progoitrin, glucoraphanin, sinigrin, neoglucobrassicin,gluconasturtiin, glucoiberin, glucobrassicanapin, and the like.

The types of plants to which the light source according to an exemplaryembodiment of the present disclosure is applied may vary. However, theremay be differences in the photosynthetic efficiency of the light emittedfrom the light source or the degree of increase in the content of theactive ingredients depending on the types of plants. The light sourceaccording to an exemplary embodiment of the present disclosure may beapplied to a plant of the Brassicaceae family. In addition, the lightsource according to an exemplary embodiment of the present disclosuremay be applied to a red radish, a red sango radish, a turnip, a cabbage,a broccoli, a rocket, an oilseed rape, a kohlrabi, a bok choy (Chinesecabbage), a red mustard, a tatsoi (Asia vitamin), a kale, and a redcabbage, which belongs to the Brassicaceae family. The types of plantsaccording to an exemplary embodiment of the present disclosure shouldnot be limited thereto or thereby, and the light source may be appliedto other types of plants. Hereinafter, for the convenience ofexplanation, the light source applied to the plant of the Brassicaceaefamily will be described as a representative example.

FIG. 1A is a plan view showing a light source for plant cultivationaccording to an exemplary embodiment of the present disclosure. FIG. 1Bis a block diagram of the light source of FIG. 1A. FIG. 2 is a blockdiagram showing a light source module for plant cultivation according toan exemplary embodiment of the present disclosure.

Referring to FIGS. 1 and 2, a plant cultivation light source module 100includes a light source 30 emitting a light that plants need, acontroller 40 controlling the light source 30, and a power supply 50supplying a power to the light source 30 and/or the controller 40.

The light source 30 may include first and second light sources 31 and 33having a spectrum peak in different wavelengths from each other. Atleast one of the first and second light sources 31 and 33 has thespectrum peak in a visible light wavelength band. Hereinafter, the firstlight source 31 having the spectrum peak in the visible light wavelengthband will be described as a representative example.

The first light source 31 may emit the light in the visible lightwavelength band. The light emitted from the first light source 31 may bea light having a wavelength band, which is mainly used in the process ofplant photosynthesis, e.g., a light in the PAR spectral range.

In the present exemplary embodiment, the first light source 31 is shownas one component; however, the first light source 31 may be implementedas one or more light emitting diodes as long as the light emittingdiodes emit the light in the visible light wavelength band that plantsare able to use for photosynthesis. Alternatively, the first lightsource 31 may be implemented as one or more light emitting diodes aslong as they emit the light having a predetermined spectrum describedlater. For example, the first light source 31 may include a lightemitting diode that substantially simultaneously emits a blue color anda red color, or may include a light emitting diode emitting a light in ablue wavelength band and a plurality of light emitting diodes emitting alight in a red wavelength band.

The second light source 33 may emit a light having a wavelength banddifferent from the first light source 31. For example, the second lightsource 33 may emit a light in an ultraviolet wavelength band,particularly, a light in ultraviolet-B wavelength band. The second lightsource 33 provides a light for the purpose of increasing the activeingredients in the plants. In addition, the second light source 33 mayalso include one or more light emitting diodes as needed.

The first light source 31 and the second light source 33 may beindividually operated. Accordingly, only one light source among thefirst light source 31 and the second light source 33 may be turned on,or alternatively, both the first light source 31 and the second lightsource 33 may be turned on or turned off. In some embodiments, the firstlight source 31 and the second light source 33 may be individuallyturned on/off and may provide the light having the predeterminedspectrum to the plants. The plants receive the light in various formsfrom the light source, i.e., the first and second light sources 31 and33, depending on their growth stage, depending on whether it is a lightperiod or a dark period, or depending on their harvesting time. Thespectrum of the light emitted from the light source including the firstand second light sources 31 and 33 will be described later.

The first light source 31 and the second light source 33 may be disposedon a substrate 20. The substrate 20 may be a printed circuit board onwhich wirings and circuits are formed to allow the first light source 31and the second light source 33 to be directly mounted thereon, however,the substrate 20 should not be limited to the printed circuit board. Theshape and the structure of the substrate 20 should not be particularlylimited as long as the first light source 31 and the second light source33 are mounted on the substrate, and the substrate 20 may be omitted.FIG. 2 is a cross-sectional view illustrating a light emitting diode,according to an embodiment of the present disclosure. However, the formof the light emitting diode is not limited thereto, but may be providedin various forms.

Referring to FIG. 2, the light emitting device may include a lightemitting structure having a first semiconductor layer 223, an activelayer 225, and a second semiconductor layer 227, and first and secondelectrodes 221 and 229 connected with the light emitting structure.

The first semiconductor layer 223 is a semiconductor layer doped with afirst conductive-type dopant. The first conductive-type dopant may be ap-type dopant. The first conductive-type dopant may Mg, Zn, Ca, Sr, orBa. In some embodiments, the first semiconductor layer 223 may include anitride based semiconductor material. In other embodiments, thesemiconductor material having the above composition formula may includeGaN, AlN, AlGaN, InGaN, InN, InAlGaN, and AlInN.

The active layer 225 is provided on the first semiconductor layer 223and corresponds to a light emitting layer. The active layer 225 is alayer which emits the light based on the band gap difference of theenergy band resulting from the intrinsic material for the active layer225 through the recombination of electrons (or holes) injected throughthe first semiconductor layer 223 and holes (or electrons) injectedthrough the second semiconductor layer 227.

The active layer 225 may be implemented with a compound semiconductor.The active layer 225 may be implemented with at least one of a groupIII-V compound semiconductor or a group II-VI compound semiconductor.

The second semiconductor layer 227 is provided on the active layer 225.The second semiconductor layer 227 is a semiconductor layer doped with asecond conductive-type dopant having a polarity opposite to that of thefirst conductive-type dopant. The second conductive-type dopant may be an-type dopant, and the second conductive-type dopant may include, forexample, Si, Ge, Se, Te, O, or C.

In some embodiments, the second semiconductor layer 227 may include anitride based semiconductor material. In other embodiments, thesemiconductor material having the composition formula may include GaN,AlN, AlGaN, InGaN, InN, InAlGaN, or AlInN.

In some embodiments, the first electrode 221 and the second electrode229 are provided in various shapes to connect with the the firstsemiconductor layer 223 and the second semiconductor layer 227,respectively. The first electrode 221 is provided under the firstsemiconductor layer 223 and the second electrode 229 is provided on thesecond semiconductor layer, but the light emitting structure of FIG. 2is not limited thereto. In some embodiments, the first and secondelectrodes 221 and 229 include Al, Ti, Cr, Ni, Au, Ag, Ti, Sn, Ni, Cr,W, Cu, or a combination thereof. The first and second electrodes 221 and229 are formed of a single layer structure, or a multi-layer structure.

In some embodiments, a vertical type light emitting diode is explained,but it is not limited thereto. The light emitting diode does notnecessarily have to be a vertical type and other types are available.

According to some embodiments, the following effects may be obtained byusing a light emitting diode instead of an existing typical lamp as alight source to apply light to a test sample.

In some embodiments, when the light emitting diode is used as the lightsource, light having a specific wavelength may be provided to anirradiation target, as compared to light emitted from the existingtypical lamp (for example, an existing UV lamp). The light emitted fromthe existing lamp has a broader spectrum in a wider area as compared tothe light emitted from the light emitting diode. Accordingly, in thecase of the existing UV lamp, it is not easy to separate only lighthaving some band of the wavelength band of the emitted light. Incontrast, the light emitted from the light emitting diode has a sharppeak at a specific wavelength and provides light of a specificwavelength having a very small half-width as comparison to light from anexisting lamp. Accordingly, it is easy to select light of a specificwavelength and only the selected light of the specific wavelength may beprovided to the target sample.

In addition, in the case of the existing lamp, although light isprovided to the test sample, it may be difficult to precisely limit anamount of light. However, in the case of the light emitting diode, lightmay be provided by exactly limiting the amount of light. Further, in thecase of the existing lamp, since it may be difficult to precisely limitthe amount of light, the irradiation time may also be set in a widerange. However, in the case of the light emitting diode, light necessaryfor the test sample may be provided within a definite time for arelatively short time.

As described above, in the case of the conventional lamp, it isdifficult to clearly determine the light irradiation amount due to therelatively wide range of wavelengths, the wide range of light quantity,and the wide range of irradiation time. To the contrary, the lightemitting diode can provide a clear light irradiation amount due to arelatively narrow range of wavelengths, a narrow amount of light, and anarrow range of irradiation time.

In addition, in the case of the existing lamp, it takes longer time toarrive at the maximum amount of light after power is turned on. To thecontrary, when the light emitting diode is used, an amount of lightinstantly arrives at the maximum amount of light since warming-up timeis hardly taken after the power is turned on. Therefore, in the case ofa light source employing the light emitting diode, the irradiation timeof the light may be clearly controlled when irradiating light of aspecific wavelength to an optical element target.

Referring to FIG. 2, the controller 40 is connected to the first lightsource 31 and the second light source 33 to control whether to operateor not the first light source 31 and the second light source 33. Thecontroller 40 may be connected to the first and/or second light sources31 and 33 via a wired connection or wirelessly. The controller 40 isconnected to the power supply 50 that supplies the power to thecontroller 40. The power supply 50 may be connected to the light sourcevia the controller 40 or may be directly connected to the light sourceto supply the power to the light source.

The controller 40 may control ON/OFF of the first light source 31 and/orthe second light source 33 such that the first light source 31 and/orthe second light source 33 emit the lights at a predetermined intensityfor a predetermine period. The first light source 31 and the secondlight source 33 may be individually operated such that the plants carryout photosynthesis with a maximum efficiency. The controller 40 mayindependently control an emission intensity or an emission time of thelights from the first light source 31 and the second light source 33. Inaddition, when the first light source 31 and/or the second light source33 include the plural light emitting diodes, the individual lightemitting diodes may be independently controlled.

The controller 40 may control the operation of the first light source 31and the second light source 33 according to a preset process oraccording to a user's input. The operation of the first light source 31and the second light source 33 may be changed in various ways dependingon the type of plants and the growth stage of the plants.

FIGS. 3A to 3C are graphs showing a spectrum of a light emitted from alight source according to an exemplary embodiment of the presentdisclosure.

The light source according to the exemplary embodiment of the presentdisclosure may emit lights having different wavelength bands from eachother depending on the growth stage of the plants. FIG. 3A shows thespectrum of the light in a predetermined period before transplanting theplants and after sowing seeds, FIG. 3B shows the spectrum of the lightin a predetermined period after transplanting the plants, and FIG. 3Cshows the spectrum of the light in another predetermined perioddifferent from the predetermined period of FIG. 3B after transplantingthe plants.

In the exemplary embodiment of the present disclosure, the seeds of theplants may be germinated during the dark period after being sowed. Forthe germination of the seeds, the dark period may be maintained forabout 1.5 days to about 3 days, for example, for about 24 hours afterthe sowing of the seeds, and only purified water may be provided to theseeds without a separate nutrient solution.

The germinated seeds may grow to sprouts under the light period and thedark period, and the sprouts may be transplanted into a cultivatingdevice after a predetermined time elapses. The germinated seeds may beunder the light period and the dark period for about 5 days to about 9days, for example, about 7 days, to grow as the sprouts, and the sproutsmay be transplanted into the cultivating device. The sproutstransplanted into the cultivating device may grow into adult plantsusing the nutrient solution.

The light period and the dark period may be variously set depending onthe types of plants and, for example, may be alternately repeated on a24-hour basis. For example, the dark period may be maintained for about6 hours to about 10 hours, the light period may be maintained for about18 hours to about 14 hours, and the dark period and the light period maybe repeated on the 24-hour basis. A light intensity in the light periodmay be within a range from about 50 to about 80 μmol/m²/s (PPFD),preferably, about 69.8 μmol/m²/s.

In some embodiments, after the seeds are germinated, a light in awavelength band that enables the photosynthesis is provided in the lightperiod until the germinated seeds grow into the sprouts before beingtransplanted. The spectrum of the light provided to the germinated seedsuntil the germinated seeds grow into the sprouts before beingtransplanted is as shown in FIG. 3A.

Referring to FIG. 3A, the light source may provide a light having aspectrum curve where a peak appears in a full width at half maximum thatis narrow at a predetermined wavelength rather than emitting a lightwith a spectrum curve having a peak in a full width at half maximum thatis substantially the same in the entire wavelength band. For example,the light source may have the peak having the narrow full width at halfmaximum and a relatively high intensity at about 660 nanometers andabout 450 nanometers. The peaks at about 660 nanometers and about 450nanometers respectively correspond to red color and blue color.

In the exemplary embodiment of the present disclosure, after beingtransplanted, the plants may grow into the adult plants under the lightperiod and the dark period until they are harvested. It may takeapproximately about 18 days to about 23 days from the transplanting tothe harvesting, and as an example, the plants may be harvested afterbeing cultivated for about 21 days (e.g., cultivating for about 30 daysafter sowing). The light period and the dark period may be variously setdepending on the types of plants and, for example, may be alternatelyrepeated on a 24-hour basis. For example, the dark period may bemaintained for about 6 hours to about 10 hours, the light period may bemaintained for about 18 hours to about 14 hours, and the dark period andthe light period may be repeated on the 24-hour basis. The lightintensity in the light period may be within a range from about 50 toabout 80 μmol/m²/s (PPFD), preferably, about 69.8 μmol/m²/s.

In some embodiments, a light having the spectrum shown in FIGS. 3B and3C may be irradiated to the plants in the light period after thetransplanting. The light having the spectrum shown in FIG. 3B may beimplemented by turning on only the first light source, and the lighthaving the spectrum shown in FIG. 3C may be implemented by turning onboth the first light source and the second light source described above.

The lights shown in FIGS. 3B and 3C are provided during differentperiods from each other. Here, the term “period” means a temporalperiod. For example, the light corresponding to FIG. 3B may be providedduring a portion of the period, and the light corresponding to FIG. 3Cmay be provided during the other portion of the period except for theportion of the period. Hereinafter, for the convenience of explanation,the period in which the light corresponding to FIG. 3B is provided willbe referred to as a “first period”, and the period in which the lightcorresponding to FIG. 3C is provided will be referred to as a “secondperiod”. In other words, only the above-described first light source maybe turned on in the first period, and both the first light source andthe second light source may be turned on in the second period.

In some embodiments, the first period or the second period are periodsin which the light having the visible light wavelength band is providedand corresponds to a predetermined period in the light period. In someembodiments, the second period is shorter than the first period.

Referring to FIG. 3B, the light source may provide a light having aspectrum curve where a peak appears in a full width at half maximum thatis narrow at a predetermined wavelength during the first period ratherthan emitting a light with a spectrum curve having a peak in a fullwidth at half maximum that is substantially the same in the entirewavelength band. For example, the light source may have the peak havingthe narrow full width at half maximum and a relatively high intensity atabout 660 nanometers and about 450 nanometers, which are mainly used forthe photosynthesis. The peaks at about 660 nanometers and about 450nanometers, respectively correspond to the red color and the blue color.In addition to the peaks respectively corresponding to the red and bluecolors, a plurality of peaks having a lower height than the peaksrespectively corresponding to the red and blue colors may be furtherprovided. In some embodiments, as shown in FIGS. 3A and 3B, the lightcorresponding to before the transplanting and the light corresponding tothe first period after the transplanting may have the same spectrum ormay have substantially similar spectrum, if not identical. However, thelight corresponding to before the transplanting and the lightcorresponding to the first period after the transplanting may havedifferent intensities from each other. For example, the intensity oflight provided to the plant after transplanting may be higher than thatof before transplanting. By way of example, the light intensity in thelight period may be within a range from about 50 to about 80 μmol/m²/s(PPFD), preferably, about 69.8 μmol/m²/s.

Referring to FIG. 3C, the light source has a spectrum similar to thelight provided in the first period in some wavelength bands during thesecond period and has a different spectrum from the light provided inthe first period in the other wavelength bands. In this case, the lightsource may provide a light having a spectrum curve with a peak appearingin a full width at half maximum that is narrow at a predeterminedwavelength during the second period rather than emitting a light havinga spectrum curve with a peak appearing in a full width at half maximumthat is substantially the same in the entire wavelength band. Forexample, the light source may have the peak having the narrow full widthat half maximum and a relatively high intensity at about 660 nanometersand about 450 nanometers, which are mainly used for the photosynthesis.Further, the spectrum of the light source has a relatively higher peakin the wavelength band other than the visible light, for example, in theultraviolet wavelength band. In some embodiments, the spectrum of thelight source has a peak with a narrow full width at half maximum at awavelength band of about 300 nm or less. The spectrum of the lightsource may have a peak with a narrow full width at half maximum at awavelength band of from about 280 to about 295. In the second period,the light source may have the same spectrum as in the first period inthe visible light wavelength band. That is, the light in the visiblelight wavelength band may be provided without being changed, and thelight in the wavelength band other than the visible light, for example,the ultraviolet wavelength band (e.g., the wavelength band ofultraviolet B) may be added.

The spectrum of the light source in each of the first period and thesecond period may be implemented by driving the light source shown inFIG. 1B. In particular, the spectrum may be implemented by independentlyor selectively turning on or turning off the first light source and thesecond light source. For example, although the light source shown inFIGS. 1A and 1B is used, only the first light source may be turned onduring the first period. In the case where the first light source isturned on, the light source may emit the light in the visible lightwavelength band, for example, the light having the spectrum shown inFIG. 3B. In the second period, the first light source and the secondlight source may be turned on. In the case where the first and secondlight sources are turned on, the light source may emit the light in thevisible light wavelength band and the light in the ultravioletwavelength band, for example, the light having the spectrum shown inFIG. 3C.

In other embodiments, the first period and the second period may bearranged in various ways depending on the growth stage and the harvesttime of the plants. For example, the first period may be arranged beforethe harvesting of the plants after the plants are transplanted. Thesecond period may be arranged adjacent to the first period and may bearranged right before the harvesting time within an overall schedule. Inother words, the first period may be continued after the transplantingof the plants, and the second period may be arranged at a time otherthan the first period right before harvesting. Then, the plants areharvested. Alternatively, the second period may be arranged between thefirst periods over one to three days right before harvesting.

In some embodiments, the plants may be cultivated under the light periodand the dark period, which are alternated for about 20 days after thetransplanting of the plants, and in this case, the light period maycorrespond to the first period. Then, the first period and the secondperiod may be sequentially provided or the second period and the firstperiod may be sequentially provided in the light period of the 21st dayafter the transplanting. In the case where the light period of the 21stday after the transplanting is about 16 hours, the first period may bemaintained for about 13 hours, and the second period may be maintainedfor about 3 hours. To the contrary, the second period may be maintainedfor about 3 hours, and the first period may be maintained for about 13hours.

This may be explained as follows. In some embodiments, the light sourcemay be turned on or turned off depending on the light period and thedark period and may be used for plant cultivation. The light source forplant cultivation is turned on during the light period and emits thelight having the spectrum with the plural peaks to the plants. The lightemitted from the light source includes the light having the wavelengthband to increase a content of a predetermined substance in the plants.

At least one of the peaks of the light emitted in the second period ofthe light period is not provided in the first period preceding orfollowing the second period. That is, the light corresponding to theultraviolet wavelength band, for example, the wavelength band equal toor smaller than about 300 nm, is provided in the second period but notprovided in the first period. By way of example, the at least one peakprovided in the second period but not provided in the first period mayhave a wavelength of from about 280 to about 295.

The other peaks except for the at least one peak, which is provided inthe second period but not provided in the first period, may be locatedin the visible light wavelength band and may be provided both in thesecond period and the first period. The other peaks except for the atleast one peak, which is provided in the second period but not providedin the first period, may include peaks provided in each of a bluewavelength band and a red wavelength band. The other peaks except forthe at least one peak, which is provided in the second period but notprovided in the first period, may appear at substantially the samewavelength as each other.

In some embodiments, the second period may be arranged right before theharvesting of the plants and may be provided in less than about 6 hours.For example, the second period may be provided for about 3 hours. Thelight provided to the plants during the second period is a continuouslight.

In some embodiments, the light source may have the structure as shown inFIGS. 1 and 2 to provide the above-described light to the plants. Thelight source may include a plurality of light emitting diodes that emitslights having different wavelengths from each other, and the lightemitting diodes may be combined with each other in various forms to emitthe light having the spectrum of the above type. For example, each ofthe first light source and the second light source shown in FIG. 1 mayeach independently include one or more light emitting diodes.

When the light source for plant cultivation is used, it is possible toindependently provide a growing environment suitable for the types ofplants even under conditions in which the sunlight is insufficient orthe sunlight is not provided. In addition, plants having a high contentof active ingredient may be easily grown.

EXAMPLES 1. Growth Conditions and Light Treatment Conditions for Plants

In the following examples, experiments were carried out on kale, whichbelongs to the Brassicaceae family, among plants as a representativeexample. The kale was grown for a total of 31 days and harvested on the32nd day. The growth conditions of the kale according to an experimentalexample are shown in FIG. 4. Hereinafter, in drawings, for theconvenience of explanation, a period during which the lightcorresponding to FIG. 3B is irradiated is shown as the first period, aperiod during which the light corresponding to FIG. 3C is irradiated isshown as the second period, and other features are described separately.

With reference to FIG. 4, a control group will be described first. Thekale was germinated in the dark period for about 2 days after beingsowed. In other words, kale seeds were first sowed into a cultivationsponge and germinated in the dark period for about 2 days to grow thekale.

The kale was grown in the light period and the dark period from day 3 today 9 after sowing, and this corresponds to an irradiation period beforetransplanting. The light having the spectrum shown in FIG. 3A wasirradiated to the kale in the light period at a light intensity of about69.8 umol/m²/s PPFD (Photosynthetic Photon Flux Density). Only thepurified water was provided to the plants after sowing and beforetransplanting.

The grown sprouts were transplanted in a deep-flow technique (DFT)hydroponic culture system on the 10th day. The transplanted kale wasgrown in nutrient solution under the light and dark periods. As thenutrient solution, Hoagland stock solution was used, and the pH of thenutrient solution was maintained at about 5.5 to about 6.5. After thetransplanting, the light period and the dark period were provided on the24-hour basis for about 21 days. On the 24-hour basis, the light periodwas maintained for about 16 hours, and the dark period was maintainedfor about 8 hours. The light having the spectrum shown in FIG. 3B wasirradiated to the kale in the light period at a light intensity of about152.8 umol/m²/s PPFD (Photosynthetic Photon Flux Density).

Control group 1 was irradiated with the light corresponding to FIG. 3Bin the light period till the 30th day from the date of transplanting.Treatment group 1 was irradiated with the light under the same conditionas the control group till the 29th day from the date of transplanting.However, treatment group 1 was irradiated with the light having thespectra shown in FIGS. 3B and 3C in the light period under a certaincondition on the 30th day from the date of transplanting.

Treatment group 2 was irradiated with the light under the same conditionas the control group till the 28th day from the date of transplanting.However, treatment group 2 was irradiated with the light having thespectra shown in FIGS. 3B and 3C in the light period under a certaincondition on the 29th and 30th days from the date of transplanting. Inthis case, the light having the spectrum shown in FIG. 3C wascontinuously irradiated during the light period of about 16 hours eachfor two days.

Treatment group 3 was irradiated with the light under the same conditionas the control group till the 27th day from the date of transplanting.However, treatment group 3 was irradiated with the light having thespectra shown in FIGS. 3B and 3C in the light period under a certaincondition on the 28th to 30th days from the date of transplanting. Inthis case, the light having the spectrum shown in FIG. 3C was irradiatedin an on and off manner for a predetermined period. As an example, theirradiation of the light having the spectrum shown in FIG. 3C wasrepeated over a period of about 3 days in a 16-hour light period in amanner in which a 5-minute irradiation is followed by a 75-minutenon-irradiation until the end of the light period.

2. Comparison of Active Ingredient Content by Irradiation with UVA andUVB

In the present experiment, effects on the plants, which are caused bythe light irradiation of the light source in the second period, wereobserved. The light irradiated in the second period in the presentexperiment has substantially the same spectrum as that of FIG. 3B in thevisible light wavelength band; however, the light irradiated in thesecond period in the present experiment has the spectra respectivelycorresponding to the ultraviolet ray A (UVA) and the ultraviolet ray B(UVB) in the ultraviolet wavelength band.

FIG. 5 shows experimental conditions in the present exemplaryembodiment, and the experimental conditions correspond to the controlgroup and treatment group 2 of FIG. 4. In detail, in FIG. 5, comparativeexample 1 corresponds to the control group of FIG. 4, and the darkperiod and the light period were respectively maintained during about 8hours and about 16 hours for last two days before harvesting. Each ofexperimental example 1 and experimental example 2 corresponds totreatment group 2 of FIG. 4. However, a light irradiated in experimentalexample 1 corresponds to the light having the peak corresponding to theUVB in the ultraviolet wavelength band of the spectrum shown in FIG. 3C,and a light irradiated in experimental example 2 corresponds to thelight having the peak corresponding to the UVA in the ultravioletwavelength band of the spectrum shown in FIG. 3C. The UVA and the UVBwere set to have different light intensities such that total energyamounts were equal to each other. In the present exemplary embodiment,the total energy amount and the light intensity of the UVA and the UVBwere values corresponding to the ultraviolet wavelength band except thevisible light, the UVB was supplied at a total energy amount of about11.52 kJ/m² and a light intensity of about 10 uW/cm², and the UVA wassupplied at a total energy amount of about 1,152 kJ/m² and a lightintensity of about 1000 uW/cm².

FIGS. 6A to 6C are graphs sequentially showing contents of chlorophylls,flavonols, and anthocyanins contained in the kale harvested on the 31stday after the date of sowing, after the light treatment was performedunder the above conditions.

Referring to FIGS. 6A to 6C, when the UVA and the UVB were applied tothe plants, both the UVA and UVB irradiation increased the content ofactive ingredients in the plants. However, even though the UVA and theUVB were provided to the plants at the same energy, the content of theactive ingredients was significantly higher when the UVB was provided tothe plants than when the UVA was provided to the plants.

Accordingly, it was found that the use of UVB as the light was moreadvantageous to increase the content of the active ingredients among theUVA and the UVB, and hereinafter, the content of the active ingredientsand the damage of the plants were examined based on the UVB.

3. Comparison of Damage to Plants and Active Ingredient Content ofPlants Due to Irradiation Dose of UVB

In the present experiment, the damage on the plants depending on anirradiation time was observed. A light used in the second period of thepresent experiment has a peak corresponding to the UVB and the visiblelight wavelength band and has substantially the same spectrum of FIG.3C.

FIG. 7 shows experimental conditions in the present exemplaryembodiment, and the experimental conditions correspond to the controlgroup and treatment group 1 of FIG. 4. In detail, in FIG. 7, comparativeexample 2 corresponds to the control group of FIG. 4, and the darkperiod and the light period were respectively maintained during about 8hours and about 16 hours for last two days before harvesting. Each ofexperimental example 3 and experimental example 4 corresponds totreatment group 1 of FIG. 4. However, in experimental example 3, thelight shown in FIG. 3C was irradiated in the light period for about 3hours, and in experimental example 4, the light shown in FIG. 3C wasirradiated in the light period for about 6 hours. The total energyamount is a value corresponding to the ultraviolet wavelength bandexcept the visible light. In the present exemplary embodiment, the totalenergy amount of the UVB in experimental example 3 was about 1.08 kJ/m²,and the total energy amount of the UVB in experimental example 4 wasabout 2.16 kJ/m².

FIGS. 8A to 8D are photographs showing experimental results ofcomparative example 2, experimental example 3, and experimental example4. In FIGS. 8A to 8D, the kale on the left side in each photographcorresponds to the control group. The photograph on the right side ofFIG. 8A is a photograph of the kale at a point in time where one day haselapsed after the light was applied according to the light conditiondescribed in experimental example 3, and the photograph on the rightside of FIG. 8B is a photograph of the kale at a point in time where oneday has elapsed after the light was applied according to the lightcondition described in experimental example 4. The photograph on theright side of FIG. 8C is a photograph of the kale at a point in timewhere 4 days have elapsed after the light was applied according to thelight condition described in experimental example 3, and the photographon the right side of FIG. 8D is a photograph of the kale at a point intime where 4 days have elapsed after the light was applied according tothe light condition described in experimental example 4.

Referring to FIGS. 8A to 8D, when the light corresponding to the UVB wasapplied for about 3 hours, the damage of the plants was not observed ata time point where one day has elapsed; however, leaf curling andbrowning phenomena were observed in the kale applied with the light forabout 6 hours at a time point where 4 days have elapsed. As a result, itwas found that the UVB causes the damage to the plants when beingapplied for a predetermined time or more, for example, for about 6 hoursor more.

FIGS. 9A to 9C are graphs sequentially showing contents of chlorophylls,flavonols, and anthocyanins contained in the kale harvested on the 31stday after the date of sowing in comparative example 2, experimentalexample 3, and experimental example 4.

Referring to FIGS. 9A to 9C, when the UVB is applied to the plants, theactive ingredients were at least maintained or the content of the activeingredients was increased. However, the tendency for the increase andthe maintenance of the active ingredients depending on time of UVBirradiation was not directly observed to a meaningful extent. Forexample, in the case of chlorophylls, the content of chlorophylls ofexperimental example 3 was significantly increased as compared with thatof the control group, but, different from experimental example 3, in thecase of experimental example 4, it is difficult to determine that thecontent of chlorophylls was significantly increased as compared withthat of the control group. In the case of flavonols, the content offlavonols in experimental examples 3 and 4 was significantly increasedas compared with the control group. However, in the case ofanthocyanins, there was no significant change in experimental example 3as compared with the control group, and the content of anthocyanins wassignificantly increased in experimental example 4.

Through this experiment, when the plants are exposed to the UVB forabout 6 hours or more to receive the energy of about 2.16 kJ/m², it wasobserved that the plants may be damaged from irradiation of light.

4. Comparison of Damage to Plants and Active Ingredient Content ofPlants Depending on Continuous Irradiation or on and Off Irradiation ofUVB

In the present experiment, influences on the plants depending on acontinuous irradiation method or an on and off irradiation method of thelight source were observed.

FIG. 10 shows experimental conditions in the present exemplaryembodiment and corresponds to the control group and treatment group 3 ofFIG. 4. In detail, in FIG. 10, comparative example 3 corresponds to thecontrol group of FIG. 4, and the dark period and the light period wererespectively maintained during about 8 hours and about 16 hours for lasttwo days before harvesting. Each of experimental example 5 andexperimental example 6 corresponds to treatment group 3 of FIG. 4.However, in experimental example 5, the light having the spectrum shownin FIG. 3C was irradiated in the light period for about 3 hours, and thelight having the spectrum shown in FIG. 3B was irradiated in the lightperiod for about 13 hours. The light irradiation in the above-describedmethod was repeated for about 3 days. In experimental example 6, thelight having the spectrum shown in FIG. 3C was provided for about 3hours in the light period, and the irradiation method in which the5-minute irradiation is followed by the 75-minute non-irradiation wasrepeated until the end of the light period in the light period of about16 hours. The light irradiation method described above was repeated forabout 3 days. Therefore, a total time during which the light is appliedin experimental example 5 is substantially the same as that inexperimental example 6, and a total energy applied in experimentalexample 5 is substantially the same as that in experimental example 6.The total energy amount was a value corresponding to the ultravioletwavelength band except the visible light. In the present exemplaryembodiment, the total energy amount of the UVB in experimental examples5 and 6 was about 1.08 kJ/m².

FIGS. 11A and 11B are photographs showing experimental results ofcomparative example 3, experimental example 5, and experimental example6. In FIGS. 11A and 11B, the kale on the left side in each photographcorresponds to the control group. The photograph on the right side ofFIG. 11A is a photograph of the kale at a point in time where the kalewas harvested when the light has been applied according to the lightcondition described in experimental example 5. The photograph on theright side of FIG. 11B is a photograph of the kale at a point in timewhere the kale was harvested when the light has been applied accordingto the light condition described in experimental example 6.

Referring to FIGS. 11A and 11B, there was almost no damage on the kalein experimental example 5 in which the light was continuously irradiatedfor about 3 hours. However, in the case of experimental example 6 inwhich the light was irradiated for about 3 hours in a flickering manner,leaf curling phenomenon in the kale was observed, and a few colorchanges were also observed. Through this, it was found that thecontinuous irradiation of the UVB was safer to the plants than theirradiation of the UVB in the on and off manner.

FIGS. 12A to 12C are graphs sequentially showing contents ofchlorophylls, flavonols, and anthocyanins contained in the kaleharvested on the 31st day after the date of sowing in comparativeexample 3, experimental example 5, and experimental example 6.

Referring to FIGS. 12A to 12C, the content of the active ingredientvaried from one active ingredient to another depending on whether thelight is irradiated in the continuous method or in the on and offmethod. In the case of chlorophylls, there was no meaningful differencein the content of chlorophylls between the control group andexperimental example 5, but in experimental example 6, the content ofchlorophylls was significantly increased as compared with the controlgroup. In the case of flavonols, the content of flavonols inexperimental examples 5 and 6 was significantly increased as comparedwith the control group. In the case of anthocyanins, the content ofanthocyanins in experimental example 5 was significantly increased ascompared with the control group. However, in experimental example 6, thecontent of anthocyanins was increased as compared with the controlgroup, but the difference was not meaningful. However, a tendency of theactive ingredient content to increase by the light irradiation wasevident, and it was found that the increase of the content of the activeingredients was greater in the case of continuous light irradiation thanin the case of on and off light irradiation.

5. Whether the Active Ingredient Content is Increased when the UVB isIrradiated Under the Dark Period

In the present experiment, influences on the plants depending on whetherthe light corresponding to the UVB is irradiated in the dark period oris irradiated in the light period were observed.

FIG. 13 shows experimental conditions in the present exemplaryembodiment and corresponds to the control group and treatment group 1 ofFIG. 4. In detail, in FIG. 13, comparative example 4 corresponds to thecontrol group of FIG. 4, and the dark period and the light period wererespectively maintained during about 8 hours and about 16 hours duringthe last day (for 1 day) before harvesting. Each of experimental example7 and experimental example 8 corresponds to treatment group 1 of FIG. 4.However, in experimental example 7, the light having the spectrumcorresponding to the UVB was irradiated in the dark period for about 3hours, and the light having the spectrum corresponding to FIG. 3B wasirradiated in the light period for about 16 hours. In this case, thelight provided in the dark period was only the UVB, and the light in thevisible light wavelength band was not provided. (The second period inwhich the UVB is provided is marked by “*”.) In experimental example 8,the light having the spectrum corresponding to FIG. 3C was provided forabout 3 hours in the light period, and the light having the spectrumcorresponding to FIG. 3B was provided for about 13 hours correspondingto a remaining light period. The total energy amount shown in FIG. 13was a value corresponding to the ultraviolet wavelength band except thevisible light. In the present exemplary embodiment, the total energyamount of the UVB in experimental examples 7 and 8 was about 1.08 kJ/m².

FIGS. 14A to 14D are photographs showing experimental results ofcomparative example 4, experimental example 7, and experimental example8. In FIGS. 14A to 14D, the kale on the left side in each photographcorresponds to the control group. The photograph on the right side ofFIG. 14A is a photograph of the kale at a point in time where one dayhas elapsed after the light was applied according to the light conditiondescribed in experimental example 7, and the photograph on the rightside of FIG. 14B is a photograph of the kale at a point in time whereone day has elapsed after the light was applied according to the lightcondition described in experimental example 8. The photograph on theright side of FIG. 14C is a photograph of the kale at a point in timewhere 4 days have elapsed after the light was applied according to thelight condition described in experimental example 7, and the photographon the right side of FIG. 14D is a photograph of the kale at a point intime where 4 day have elapsed after the light was applied according tothe light condition described in experimental example 8.

Referring to FIGS. 14A to 14D, in the case where the light correspondingto the UVB was applied to the plants in the dark period, the damage onthe plants was not observed at the time point where one day has elapsed,however, leaf curling and browning phenomena were observed in the kaleat the time point where 4 days have elapsed. In the case where the lightcorresponding to the UVB was applied to the plants in the light period,the damage of the plants was not observed at both time points where oneday has elapsed and where 4 days have elapsed. Through this, it wasfound that the UVB easily damages the plants in the dark period ratherthan in the light period.

FIGS. 15A to 15C are graphs sequentially showing contents ofchlorophylls, flavonols, and anthocyanins contained in the kaleharvested on the 31st day after the date of sowing in comparativeexample 4, experimental example 7, and experimental example 8.

Referring to FIGS. 15A to 15C, in the case where the light correspondingto the UVB was applied to the plants in the light period or the darkperiod, the content of chlorophylls and the content of flavonols amongthe active ingredients were significantly increased. However, in thecase of anthocyanins, no meaningful increase in the active ingredientcontent was found.

6. Whether UVB Irradiation Under the Light Cycle Increases thePredetermined Substance Content of Various Cruciferous Plants

In this experiment, the effects of cruciferous plants were observed whenno UVB light was irradiated and when irradiated in the light period. Tothis end, in the following examples, additional experiments wereconducted on a tatsoi (Asia vitamin), mustard, and broccoli amongcruciferous plants.

FIG. 16 shows experimental conditions in an embodiment, in whichcomparative examples and experimental examples correspond to comparativeexample 4 and experimental example 7 of FIG. 13, respectively, and theexperimental conditions are the same between each other. FIGS. 17A to17C are graphs sequentially showing contents of chlorophylls, flavonols,and anthocyanins contained in tatsoi, mustard, and broccoli harvested onthe 31st day after the date of sowing, after the light treatment wasperformed in comparative examples and experimental examples according tothe experimental conditions of FIG. 16.

Referring to FIGS. 17A to 17C, in the case of the experimental exampleirradiated with UVB in the light period, the content of thechlorophylls, flavonols, anthocyanins are all increased compared to thecomparative example not irradiated. In particular, in the case ofchlorophylls, a significant increase of the contents for tatsoi (Asiavitamin) and mustard was observed in the experimental example with UVBirradiation in the light period. In the case of flavonols, a significantincrease of the contents for all of tatsoi, mustard, and broccoli wasobserved in the experimental example with UVB irradiation in the lightperiod. In the case of anthocyanins, the contents for tatsoi, mustardand broccoli were not so remarkably increased, but still considerablyincreased.

FIGS. 18A to 18C are photographs showing the experimental results of thecomparative example and the experimental example according to theexperimental conditions of FIG. 16. Referring to FIGS. 18A to 18C, inthe case of the experimental example irradiated with UVB in the lightperiod, no special change in appearance, for example, leaf-curling,browning, and death was not found compared to the comparative examplewhich is not irradiated. As could be seen from the above-describedembodiments, the light source according to the exemplary embodiment ofthe present disclosure provides the light having the specific wavelengthto the adult plants in a specified method during the predeterminedperiod, and thus the plants with the high active ingredient content maybe obtained.

The light source according to the exemplary embodiment of the presentdisclosure may be used for plant cultivation, and in detail, the lightsource may be applied to a plant cultivation device and a greenhouseeach in which a light source is installed.

FIG. 19 is a perspective view showing a cultivation device according toan exemplary embodiment of the present disclosure. The cultivationdevice shown in FIG. 19 corresponds to a small-sized cultivation device;however, it should not be limited thereto or thereby.

Referring to FIG. 19, the cultivation device 100 according to theexemplary embodiment of the present disclosure includes a housing 60having an inner space capable of growing the plants and a light source30 provided in the housing 60 to emit a light.

The housing 60 provides an empty space therein within which the plantsmay be provided and may be grown. The housing 60 may be provided in abox shape that is capable of blocking an external light. In someembodiments, the housing 60 may include a lower case 61 opened upwardand an upper case 63 opened downward. The lower case 61 and the uppercase 63 may be coupled to each other to form the box shape that blocksthe external light.

The lower case 61 includes a bottom portion and a sidewall portionextending upward from the bottom portion. The upper case 63 includes acover portion and a sidewall portion extending downward from the coverportion. The sidewall portions of the lower case 61 and the upper case63 may have structures engaged with each other. The lower case 61 andthe upper case 63 may be coupled to each other or separated from eachother depending on a user's intention, and thus a user may open or closethe housing 60.

The housing 60 may be provided in various shapes. For example, thehousing 60 may have a substantially rectangular parallelepiped shape ormay have a cylindrical shape. However, the shape of the housing 60should not be limited thereto or thereby, and the housing 60 may beprovided in other shapes.

The housing 60 provides an environment in which the plants providedtherein may be grown. The housing 60 may have a size that is capable ofaccommodating a plurality of plants provided and grown therein. Inaddition, the size of the housing 60 may be changed depending on a useof the plant cultivation device 100. For example, in a case where theplant cultivation device 100 is used for a small-scale plant cultivationat home, the size of the housing 60 may be relatively small. In a casewhere the plant cultivation device 100 is used for commercial plantcultivation, the size of the housing 60 may be relatively large.

In some embodiments, the housing 60 may block the light such that theexternal light is not incident into the housing 60. Accordingly, a darkroom environment, which is isolated from the outside, may be providedinside the housing 60. Therefore, the external light may be preventedfrom being unnecessarily irradiated to the plants provided inside thehousing 60. In particular, the housing 60 may prevent an externalvisible light from being irradiated to the plants. However, in somecases, the housing 60 may be designed to be partially opened, and thusthe housing 60 may receive the external light as it is.

The space inside the housing 60 may be provided as one space. However,this is for the convenience of explanation, and the space inside thehousing 60 may be divided into a plurality of compartments. That is,partition walls may be provided in the housing 60 to divide the spaceinside the housing 60 into the compartments.

The light source provides the light to the plants in the space of thehousing 60. The light source is disposed on an inner surface of theupper case 63 or the lower case 61. The light source may be disposed onthe cover portion of the upper case 63. The light source disposed on aninner surface of the cover portion of the upper case 63 is shown,however, it should not be limited thereto or thereby. For example, thelight source may be disposed on the sidewall portion of the upper case63. As another example, the light source may be disposed on the sidewallportion of the lower case 61, e.g., on an upper end of the sidewallportion. As further another example, the light source may be disposed onat least one of the cover portion of the upper case 63, the sidewallportion of the upper case 63, and the sidewall portion of the lower case61.

A culture platform 70 may be provided in the space of the housing 60 tocultivate the plant easily, for example, for facilitating a hydroponicculture. The culture platform 70 may include a plate-shaped plate 71disposed at a position spaced apart upward from the bottom portion ofthe housing 60. Through-holes 73 with a uniform size may be providedthrough the plate 71. The culture platform 70 may be provided to allowthe plants to be grown on an upper surface of the plate 71 and mayinclude a plurality of through-holes 73 to allow water supplied theretoto be drained when the water is supplied. The through-hole 73 may beprovided in a size such that the plants do not slip through. Forexample, the through-hole 73 may have a diameter smaller than theplants. A space between the culture platform 70 and the bottom portionof the lower case 61 may serve as a water tank in which the drainedwater is stored. Accordingly, the water drained downward through thethrough-hole 73 of the culture platform 70 may be stored in the spacebetween the bottom portion of the lower case 61 and the culture platform70.

However, in some embodiments, plants in the family Poaceae may also becultivated by methods other than the hydroponic culture method. In thiscase, water, a culture medium, and soil may be provided in the space ofthe housing 60 to supply the water and/or nutrients necessary for theplants in the family Poaceae, and the housing 60 may serve as acontainer. The culture medium or the soil may contain the nutrients forthe plants to grow, such as potassium (K), calcium (Ca), magnesium (Mg),sodium (Na), and iron (Fe). The seeds may be provided while beingimbedded in the culture medium or may be placed on a surface of theculture medium depending on its type.

The culture platform 70 may have a size and a shape, which varydepending on the shape of the housing 60 and the providing manner of afirst light source and a second light source. The size and the shape ofthe culture platform 70 may be configured to allow the plants providedon the culture platform 70 to be placed within an irradiation range ofthe light irradiated from the first light source and the second lightsource.

The housing 60 may include a water supply unit disposed therein tosupply water to the plants. The water supply unit may be configured tobe disposed at an upper end of the housing 60, e.g., on the innersurface of the cover portion of the upper case 63, and to spray wateronto the culture platform 70. However, the configuration of the watersupply unit should not be limited thereto or thereby, and theconfiguration of the water supply unit may vary depending on the shapeof the housing 60 and the arrangement of the culture platform 70. Inaddition, the user may directly supply the water into the housing 60without a separate water supply unit.

The water supply unit may be provided in a singular or plural number.The number of the water supply units may be changed depending on thesize of the housing 60. For instance, in the case of the relativelysmall-sized plant cultivation device for the home usage, one watersupply unit may be used since the size of the housing is small. In thecase of the relatively large-sized commercial plant cultivation device,the plural water supply units may be used since the size of the housing60 is large. However, the number of the water supply units should not belimited thereto or thereby and may be provided in a variety of positionsin various numbers.

The water supply unit may be connected to a water tank provided in thehousing 60 or a faucet outside the housing 60. In addition, the watersupply unit may further include a filtration unit such that contaminantsfloating in the water are not provided to the plants. The filtrationunit may include a filter, such as an activated carbon filter or anon-woven fabric filter, and thus the water passing through thefiltration unit may be purified. The filtration unit may further includea light irradiation filter. The light irradiation filter may removegerms, bacteria, fungal spores, and the like, which are present in thewater, by irradiating an ultraviolet light or the like to the water. Asthe water supply unit includes the above-mentioned filtration unit,there is no possibility that the inside of the house 60 and the plantsare contaminated even when water is recycled or rainwater or the like isdirectly used for the cultivation.

The water provided from the water supply unit may be provided as plainwater itself (for example, purified water) without additional nutrients,however, it should not be limited thereto or thereby, and the waterprovided from the water supply unit may contain nutrients necessary forthe growth of the plant. For example, the water may contain a material,such as potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), andiron (Fe), and a material, such as nitrate, phosphate, sulfate, andchloride (Cl). For instance, Sachs's solution, Knop's solution,Hoagland's solution, or Hewitt's solution may be supplied from the watersupply unit.

According to the exemplary embodiment, the plants may be cultivatedusing the light source.

A plant cultivation method according to an exemplary embodiment of thepresent disclosure may include germinating a seed of the plants andproviding the light in the visible light wavelength band to thegerminated plant. The light provided to the plants is emitted from thelight sources according to the above-described embodiments, and thelight in the visible light wavelength band may include at least two orthree lights among first, second, third, and fourth lights havingdifferent light spectra from each other.

Although the exemplary embodiments of the present disclosure have beendescribed, it is understood that the present disclosure should not belimited to these exemplary embodiments but various changes andmodifications can be made by one ordinary skilled in the art within thespirit and scope of the present disclosure as hereinafter claimed.

Therefore, the disclosed subject matter should not be limited to anysingle embodiment described herein, and the scope of the present presentdisclosure shall be determined according to the attached claims.

We claim:
 1. A plant cultivation light source, comprising: two or morelight sources configured to be turned on or turned off depending on alight period and a dark period of a selected plant, the light periodcomprising a first period and a second period and the first periodpreceding or following the second period, wherein one or more lightsources are turned on during the light period and the turned on lightsources are operable to emit a light having a spectrum with a pluralityof peaks to the selected plant to increase a content of a predeterminedsubstance in the selected plant, and wherein the one or more lightsources are turned on or turned off such that the spectrum of the lightis adjusted to provide at least one peak of the peaks of the light inthe second period and not in the first period and to make the rest ofpeaks appear at substantially the same wavelength in the second periodand the first period.
 2. The light source of claim 1, wherein the atleast one peak provided in the second period and not provided in thefirst period appears at a wavelength equal to or smaller than about 300nm.
 3. The light source of claim 2, wherein the at least one peakprovided in the second period and not provided in the first period has awavelength of from about 280 to about 295 nm.
 4. The light source ofclaim 3, wherein the second period is shorter than the first period. 5.The light source of claim 4, wherein the second period is less thanabout 6 hours.
 6. The light source of claim 3, wherein the light iscontinuously emitted from the light source during the second period. 7.The light source of claim 1, wherein the dark period and the lightperiod are repeated on a daily basis.
 8. The light source of claim 1,wherein the predetermined substance comprises at least one ofchlorophylls, flavonols, and anthocyanins.
 9. The light source of claim1, wherein the other peaks except for the at least one peak provided inthe second period and not provided in the first period are provided in avisible light wavelength band.
 10. The light source of claim 9, whereinthe other peaks except for the at least one peak provided in the secondperiod and not provided in the first period comprise peaks respectivelyprovided in a blue wavelength band and a red wavelength band.
 11. Thelight source of claim 1, wherein the light source comprises a pluralityof light emitting diodes emitting lights having different wavelengthsfrom each other.
 12. The light source of claim 11, wherein the lightemitting diodes comprise: a first light emitting diode providing thelight corresponding to the at least one peak provided in the secondperiod and not provided in the first period; and a second light emittingdiode providing the light corresponding to the other peaks except forthe at least one peak.
 13. A plant cultivation device, comprising: ahousing in which a selected plant is provided: a light source providedin the housing to irradiate a light to the selected plant; and acontroller operable to control the light source, wherein the controlleroperates to turn on or turn off the light source depending on a lightperiod and a dark period of the selected plant, and wherein when thelight source is turned on in the light period, the light source emits alight having a spectrum with a plurality of peaks to the selected plantto increase a content of a predetermined substance in the selectedplant, and wherein the controller operates to control turn-on orturn-off of the light source such that the light source generates thelight having the spectrum having: at least one peak of the peaks of thelight emitted in the second period of the light period is not providedin the first period preceding or following the second period, and theother peaks except for the at least one peak provided in the secondperiod and not provided in the first period appear at substantially thesame wavelength in the second period and the first period.
 14. The plantcultivation device of claim 13, wherein the at least one peak providedin the second period and not provided in the first period appears at awavelength equal to or smaller than about 300 nm.
 15. The plantcultivation device of claim 13, wherein the controller controls the darkperiod and the light period to be repeated on a daily basis.
 16. Theplant cultivation device of claim 13, wherein the predeterminedsubstance comprises at least one of chlorophylls, flavonols, andanthocyanins.
 17. A method of cultivating a selected plant, comprising:controlling a light source to turn on, or turn off depending on a lightperiod and a dark period of a selected plant, wherein the light periodcomprises a first period and a second period, the first period followingor preceding the second period; generating a light having a spectrumwith a plurality of peaks to be provided to the selected plant in alight period; adjusting the spectrum of the light to have at least onepeak of the peaks of the light emitted in the second period of the lightperiod and not provided in the first period and such that the rest ofpeaks appear at substantially the same wavelength in the second periodand the first period; and irradiating the light having an adjustedspectrum to an adult plant immediately prior to harvesting the adultplant to increase a content of a predetermined substance in the plant.18. The method of claim 17, wherein the light emitted in the secondperiod of the light period is continuously provided.
 19. The method ofclaim 18, wherein the second period is shorter than the first period.20. The method of claim 18, wherein the light emitted in the secondperiod of the light period has a wavelength band corresponding to a UVB.